The work described herein consists of the development of a large scale purification procedure for the isolation of intact vitellogenin mRNA from the livers of estrogen-treated roosters. The purified mRNA has been translated into a full-size vitellogenin polypeptide and its size has been determined both by electrophoresis in agarose gels and by contour length measurements in the electron microscope. Vitellogenin complementary DNA of high specific activity has been prepared and used as a probe to examine the kinetics of induction of vitellogenin mRNA synthesis in rooster liver in response to treatment with estrogen. BIBLIOGRAPHIC REFERENCES: Mullinix, K.P., Wetekam, W., Deeley, R.G., Gordon, J.I., Meyers, M., Kent, K.A., and Goldberger, R.F.: Induction of vitellogenin synthesis by estrogen in avian liver: Relationship between level of vitellogenin mRNA and vitellogenin synthesis. Proc. Nat. Acad. Sci. USA 73: 1442-1446, 1976. Wetekam, W. Deeley, R.G., Mullinix, K.P., Gordon, J.I., Meyers, M., Kent, K.A., and Goldberger, R.F.: Effect of estrogen on gene expression: Vitellogenin synthesis may be regulated at the level of transcription and translation. In Nierlich, D.P., Rutter, W.J., and Fox, C.F. (Eds.): Molecular Mechanisms in the Control of Gene Expression. New York, Academic Press, 1976, pp. 349-354.